Dimpling machine



jam. 49 W-g. H, R MSCI-1ER 2,457,992

DIMPLING MACHINE Filed Jan. 15, 1945 6 She'ets-Sheet l` l l a 56 45 44 Y A -V b' Z O o 0 I l V 39 58 ,liti

wBY 071% ATTORNEY Jan. 4, 1949. H. R. FISCHER 25i7 DIMPLING MACHINE L Filed Jan. l5, 1945 6 Sheets-Sheet 2 INVENTOR ATTORNEY INVENTOR 6 .Sheets-Sheet 3 H. n. FISCHER DIMPLING MACHINE Jan. 4, 194

Filed Jan, 15, 1945 Jan. 4, 1949.

Filed Jan. l5, 1945 H. R. FISCHER DIMPLING MACHINE 6 SheetsfSheet 4 BY /9 M MORNEY Jan. 4, 1949.' H. R. FlsHER 2,457,992

DIMPLING MACHINE Filed Jan. 15, 1945 I6 Sheets-Sheet 5 .mau

ATTORNE Jan. 4, 1949. H, R. HSCHER 2,457,992

y DIMPLING MACHINE Filed Jan. 15, 1945 T1-rali.

6 Sheets-Sheet 6 TTORNEY Patented `fan. 4, 194i) UNITED STATES PATENT i OFFICE DIMPLING MACHINE vHoward R. Fischer, Detroit, Michl., assignor to` Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application January 15, 1945, Serial No. 572,839

zo Claims. (o1. 415a- 21)` This invention relates to automatic dimpling machines with particularreference to apparatus or attachments adapted to be applied to conventional riveting machines for quickly converting them into machines for dimpling work sheets from the topside and alternatively from the underside thereof.

a The main object of the invention is to provide automatic means for dimpling metal work sheets from above or below the latter .by mounting upon a riveting or dimpling machine a special type of dimpling tool and equipment which is partly `reversed in position for topside dimpling from the position of said tool and equipment when arranged for underside dimpling.,

Another object is to `provide a riveting or dimpling machine with dimpling equipment which also includes a movable `member and` associated micro-switch operated thereby for stopping operation of the machine at the end of the dimpling stroke in order to produce uniform dimpling..

A further object is to have dimpling equipment which is accurately adjustable for uniformly dimpling work sheets of various gauges in predetermined manner.

It is also an object of the invention to have such equipment adapted to cooperate with a starting switch circuit which is arranged to cause only one cycle of operation for each time it is closed without regard to the length of time said circuit remains closed. `According to a feature of this invention the starting circuit includes two Switches arranged in series, one being depressed by the foot of the operator andthe other -being closed by the weight of the sheetV metal when properly positioned on the dimpling die.

Other objects and advantages of the invention are set forth more fully in the following specification so as to become obvious when the latter is considered in conjunction with the accompanying drawings, in which:

Fig. 1 is a side elevation of a machine having a yoke of the type commonly employed for riveting, but equipped with the automatic dimpling attachment embodying the invention when arranged for topside dimpling of metal work sheets;

Fig. 2 is another elevational View of the same machine as seen from the opposite side. the base portion being omitted;

Fig. 3 is a fragmentaryelevation. of the uppermost part or tool holder of the topside dimpling equipment; Fig. 4 is a section of the lowest portion `of the dimpling equipment including a switch casing with `2 a micro-switch andassociated parts in operative position; y

Fig. 5 isan elevationipartly in section. of the topside dimpling equipment alone showing only fragments ofthe jaws ofthe dimpling or riveting machine;

Fig. 6 is a similar elevation` partly in section of the dimpling equipment arranged for underside dimpling, theA lower portion of the micro-switch andits casing `being broken off;

Fig. '7*` is a fragmentary sectionof the portions of the undersidedimpling equipment of Fig. 6 which are generally exposed between the jaws of the machine; Y

Fig. 8 is also a fragmentary section` of the portions ofthe topside dimpling equipment of Fig. 5 generally exposed between the jaws of the machine and disposed in initial operative position;

Fig. 9 is a similar section of the same equipment in operated position with a work sheet in place in fully dimpled condition; y y

Fig. 10 is a circuit diagram of the machine and the dimpling equipment when considered asan electrical system, the latter beingshown in. initial idle or open circuitcondition; i

.,Fig. 11` illustrates the `same circuit diagram with the main switch `closed and the footswitch depressed; j K- j i.

Fig. 12,Y is another viewof the `circuit diagram when the machine is carrying out adimpling operation; and

Fig. 13is a final condition of said circuit diagram when the, dimpling operationjis completed and the circuithas been automatically opened. i Figs. 1` and 2 are drawn to a `much smaller scale than Figs;` 5 and6, while Figs. 3, 4,7, Sand 9 are drawn to twice the size ofFigs. 5 and 6.

UIn, dimpling machines and] apparatus it is desirable to have thelatter capable of being arrangedjfor; dimpling metal work sheets from` the upper side thereof and also `for dimpling said sheets from theunderside, certain conditions in the industry requiring this type of dimplingland atother times the other type of dimpling in order to save time and effect various economies and conveniences; Especially is it desirable to be in apositionto adjust the dimpling equipment accurately so that fwhether topside or underside dimpling is performed it is uniformly and perfectly carried out to allow subsequent satisfactory riveting of said sheets. l l j Itis therefore proposed to equip a dimpling or riveting machine ofthe general type disclosedin the copendingy application of Howard R. Fischer and James `\A. Roberts, Serial No.:51l,068J filed rlecember 13, 1943, for a Compression riveter, with special attachment means which fulfill the foregoing objects in making the machine adapted either for topside dimpling or for underside dimpling by using the major portion of the same equipment in both cases, with the machine equally effective in either case to produce repeated dimpling to exactly Athe same degree or extent.

In industries dealing with sheet metal, as for example that occupied with the production of airplanes, dimpling and riveting the metal sheets or skin form a large part of the work to be accomplished and in order to set flush type Vrivets to best advantage in said 'sheets which are usually of aluminum and `aluminum alloys, the sheets are first drilled and dimpled to facilitate proper setting of the rivets, the work being necessarily carefully done to avoid damaging the metal. It is therefore most desirable that the dimpling be uniformly and carefully doneA l phere during night; :not to mention `that it .is

ldesirable to dimpletthe workfautomatically and repeatedly to save time andincrease production.

Referring again to the drawings, a dimpling or riveting machine generally indicated `at 2lil consists mainly of a more or less massive Lyoke 2l terminating at the frontof the machine in opposed jaws 22, 23 and supported rigidly on a column 24 xed l.upon a wide ibase k25. .As the yoke is rather deep in order .to accommodate work pieces of large size, the jaws yhave considerable length and during operation are lunder apprecia-ble strain, and hence the yoke as a whole is made of material having great strength, 'toughness and elasticity, such as lboiler 1p1'ate1steel in order to permit the development of great dimpling pressures with consequent measurable spreading apart of the jaws l22 'l23`but without straining the yoke beyond its elastic limit or endurance limit. In the upper jaw is -mounted a plunger 26 (Fig. 2) to the lower end of which is attached a set or tool holder 21,1while above the plunger is an operating cam lever 528 pivoted at 29 in the superstructure or frame 43i above the yoke, which lever in lowered-position is adapted to exert pressure on ythe 4upper end of said plunger to depress the latter. The superstructure is continued rearwardly in the 'form of a cylinder 32 in whichpiston 33 is reciprocable and provided with a piston rod 34 with tract-ion rollers 35 at the outer end of the'latter, the upper roller engaging against upper track 3'6 `asa "re-v action basis on the one hand and on theother hand upon the upper stra-ight surface of cam lever 28, it being obvious that when the piston; rod and rollers thereof are withdrawn re'ar'.

- 4 the specific details of these parts are more' or less conventional and form no actual parts of the invention as such, it may suffice to state that the piston rod, piston and mounting of the rollers may follow known principles or the corresponding features in the mentioned copending application. On the other hand the superstructure lor frame 3l as well ias cylinder 32 rigidly secured thereto ane fixed yupon the upper yoke extension 38 by screws or bolts 39 while a front plate 4I is attached to the front of the ,yoke extension and of frame 3| by screws or the like (not shown) to form a closure for the frame -an'd further support therefor.

Incidentally the front plate also includes the casing 42 pivotally "supportingstop switch lever 43 which is disposed in the path ofthe front end of piston rod 34 and rocked by the latter to operate a button 44 of stop Vswitch 45 to stop the piston in case said piston and piston rod should overrun their proper stroke Vin the forward 'direction `.when executing a power stroke. This Aoperation lwill be referred :to in vconnection with the :circuit diagrams of Figs. 10` to 13.

The :pressure fluid, which Ais preferably compressed air, is conducted by hose 46 to fixture 4l (Fig. 1) on the machine from an appropriate outside source 'of pressure huid. ,From vthe xture vthe pressure fluid .passes through the r'air line oiler 43 and a pressure kregulator r49 .fcontrolled by a manual 'regulating screw :50, .past pressure gauge 5l and :thence :up through Yhose line .52 to the valve .housing15'3 .(Fig'. 2') Within the latter the control valve generally indicated diagrammaticallyat 54 in Figs. 1'0 to 13 is'smov'- able to control the supplyiof fthe pressure 'fluid to the cylinder 3'2 bythe armature or core 55 aof solenoid device 56 surmounting the..superstrurl---A ture, certain detail being omitted ,as ksuperfluous here, but the operation Ain general will `be set forth in connection with the circuit diagrams alreadyreferred VVto which include the essentials of the system as a whole'involved in the machine.

From the'foregoing it is evident 'that W-henithe control valve is operated to allow the .cylinder at'o exhaust rearwardly vof `the ipiston the :spring 31 (Fig. 2) will raise -plunger 26 .and thereby 'raise cam lever 28 to ya .higher inclined finitial position vwhile ,pressure .fluid is allowed to 'operate in front of the piston ,so that'the latter with its rod and rollers will -be returned `to rearward initial position in which-the rollers `are disposed directly above the depression orV clearance 5.1 in the'cam lever. When the piston rod and rollers :35 occupy the rearward position, 'spring 31 is eifective to raise plunger 26-and by the .flatter the 'cam .lever to the raisedinclined position (not s-hown.) :ready for a new power stroke.

It has already been'mentioned'that duringlop eration when'considerable dimplingspressures are produced, the yoke jaws 22 and `23 are :m'easurab'ly spread apart by the reaction of such .pressures and this eectis therefore'used togo'odadvantageby attaching the lower forward ,end .58 of a wardly, the plunger 26 is relieved of the pressure of the lever and allowed to rise t'o initial position under the influence of 'a .restoring spring 31, as will be further explained.

As may `be noted in Fig. 2, rollers 35 are de- U-shaped deector plate 5.9 `(Fig. 1) to the ,lower jaw "23 by screws 6| or the like and loosely `retaining the intermediate lportion in proximate association'with the yoke "2| by a 'screw ".62, the latter merely serving as a vsupport or Aguf'trd 'to prevent the plate from being accidentally bent outward away from the yoke. The upper 'forward enses lprojects int-0 a switch box s4 and within theulatter overhangs the lower "short end 'e5 of a. deflection switch lever tt'preieratiy pivttea .on knife-edge fulcrum si supported en the upper jaw 22. The upper long arm `68 ofthe deflectionswitch lever is spaced a predetermined small distance from the trigger, depressible button, or plunger 69 of a deflection plate microswitch 10 within the switch box. The switch 10 ismounted onjaw 22 for limited movement forward `and rearward in response to the turning of an adjusting knob 10a (Fig. l). By this means the operator may regulate `the distance between arm 58 and button 69 and thereby predetermine the extent of swinging movement of lever 66 required for the actuation of the microswitch 10. For a more complete description of the mounting for switch `10, reference is made to the copending application,` aforesaid. 'Ihe electrical conductors between the switch and the relay box 1| on the rear of yoke 2| (Fig. 2) extend through cable 12 (Fig. 1), while from said relay box a further cable 13 extends up to solenoid 56. A cable 14 also extends down from the relay box to a foot switch 15 having a pedal 18 which when depressed by the foot of the operator closes the operating circuit associated therewith, a further cable 11 bringing electric current to the machine from an outside source.

The topside dimpling equipment will first be considered and then the operation thereof after which the underside dimpling equipment will be dealt with in due order. In the set holder 21 (Figs. 8 and 9) is mounted a punch holder 18 with shank 19 thereof secured in the set holder by a screw 8|` extending up into and preferably secured to the plunger 26 in more or less conventional manner (not shown), the hexagonal flange 82 (Fig. 3) serving the double purpose of forming a stop against the lower end of set holder 21 and a means adapted for engagement by a wrench when screwing the punch holder in place or removing the same. The punch holder 18 rigidly follows the movements of the set holder and carries a skirted dimpling punch 83 with the shank portion 84 thereof secured in the lower end of punch holder 18 by aset screw 85. y

Exteriorly on the punch holder are mounted a pressure pad or cushion 89 of rubber or other resilient plastic material confined between a pressure pad washer 81 and a pressure pad plate 88. The washer is retained in place by a split retaining ring 89 slidably seated in the lower end of a wide annular groove 9| on the set holder, while an adjusting nut 92 for the pressure pad is screwed down upon the thread 93 against plate 88 for adjusting the pressure pad to the desired degree oi compression for producing proper resistance` during operation. The punch has an intermediate flange 94 engaging against the lower end of the punch holder to properly locate and back the punch and beneath which is xed the dimpling punch sleeve 95 held on the punch by set screw 96 and spaced from flange 94 by one or more punch sleeve shims 91, the sleeve 95 being one of a series of sleeves of different length individually adapted to cooperate with the frusto-conical portion 98 of the punch to dimple sheets of various gauges. Exteriorly of the sleeve 95 is a slidably mounted skin support sleeve 99 extending upwardly about punch flange 94 and the lower end of punch holder 18 against retaining ring 89 and downwardly a small distance to approximately the lower end of the frusto-coni cal portion 98 on the punch. Sleeve 99 is retained in assembled relation with the parts just enumerated by a sleeve retaining ring in a second groove on the punch holder. Thus if the pilot pin |0| of the punch enters a hole in the metal work sheet |02` to eneagethe dimpling portion 98 withsaidvworksheet, thelowereend of skin support sleeve99 willalso make, contact with `the work sheet and be forced ,upward by the latter during the dimplingoperation to compress pad` 86 while liftingmring 89 toward the upper portion of groove 9|. .It.wil1 be .understood that the `punch 8 3 may beappliedeither to a single sheet |92 orto a pairof overlapping sheets having registering rivet holes to receive thepilo'tpinll. n ,A y u y Complementing the dimplingmunch and its assembly supprted by the upper jaw 22 is a lower die holderior dimpling dolly [03supportedin the lower jaw 23 with its associated parts which a-re now to be described. The dolly |03 is secured in the dolly sleeve `|04 by screws |05 and |06, the sleeve |04 being rigidly secured in the adjustable dolly spindle or screw |01 which `is screwed into internally threaded bushing |08 fixed in the lower yoke jaw. y The dolly |03 is surmounted by dimpling die |09 which has `a downwardly extending hollow shank occupy,- ing` the upper end of a bore ||2 in said dolly and secured in place by a set screw ||3'., The upper face of the dimpling die has a recess ||4 to provide clearance for the metal displaced downwardly bythe conical dimpling portion 98 of punch 83 above (Fig. 9). Within bore |5 in die |09 is a slidably mounted pilot pin ||6 normally projecting with its upper end above die |09 and terminating atthe lower lend in a head or retaining shoulder ||1 which prevents accidental removal or loss of the pin from the die and rests on the upper ends of the prongs ||8 (one shown) of a bifurcated pilot pin sleeve ||9. The latter l in turn rests on a pilot pin sleeve washer |2| resiliently maintained in extreme raised position by the upper end of pilot pin return spring |22, the lower end ofthe latter being conned by the bottom |23 of the dolly sleeve |04. A.

Surrounding the dimpling ydie |09 in slidable relation therewith is a dimpling sleeve |24 normally projecting with its upper edge a slight distance above the general upper level of the dimpling die and at its lower end terminating immediately above the short sleeve or ring |25 through the open bottom slots |28 (Fig. 9) of which a crossbar 21 extends, the latter also extending transversely through side slots |28 in the dimpling dolly as well as between the prongs ||8 already mentioned.` The ring |25 has a peripheral groove (not shown) registering with the end slots |29 in the crossbar and the latter is retained in assembled association with the ring by a retaining wire 3| or the like. The mentioned dimpling sleeve |24 has a cut away portion |32 y exposing part of the side of the dimplingl die and of the upper portion of the 'dimpling dolly` to provide ready access to said die during operation, and interiorly has a counterbore |33 terminating at an intermediateshoulder |34 adapte-d to engage against shoulder |35 to form a stop upon the wide portion |36 on said dimpling dolly to limit downward movement of the dimpling sleeve to normal `operation thereof. The crossbar |21 rests upon the upper end of a long push rod |31 which is guided in the tubular Apunch die bolt |38 (Fig. 8) screwed by its upper threaded end |39 into thebottom |23 of dolly sleeve |04 to hold the latter in placer inthe dolly spindle |01, The lower end of the bolt has a hexagonal head `|4| rigid therewith (Fig. 4) engaging against the lower. end of a reduced extension |42 of thedolly spindle |01 which facilitates turning the bolt, the

latter Ibeing thus held rigid betwerlcthe :spinale extension and theldolly sleeve |04.

The dolly spindle extension 142 has fa die' adju'sting screw knob |43 fixed thereto'b'y se't scr-'ew |44 by which to rotatablyladjust 'thegdi'e adjusting screw, thesame extension 142 having a transverse scale |45 (Fig. 5) exposed `in afcii't'out portion 14S below jaw 23 in bushing sl'il `which is upper endv of theswitch housingwhich surrounds l the mentioned annular extension hasan inwardly directed ilange or rib B53 tting rotatably in "a corresponding groove '|56 in the -annular eir'tension and serving to retain the housing in -ele'ctive association with said extension while allowing the dolly spindle orscrew and the extension of the latter to be rotated for adjustingfthe dirnpling die without also rotatingthelswitch housing. In other words the housing his supported in virtual noating or suspended ycondition `on the spindle extension, and as a cable extends from the lower portion thereof `torelay box'l on the yoke, thehousing is prevented from rotating with the spindle. The switch housing is made of two halves secured together by screws y|5'l and clamp thelower end of the cable #between them with the conductors |58 entering the housing from the cable and' being connected to the micro-switch, the other end of the 'cable terminating in the switch cable plug or connector |59 detachably plugged into the relay box receptacle |6| (Fig` 2). The connections in v1olf-:tail as well as the relays associated wththe relay box will presently be explained'when Considering the circuits of the diagram gures.

-vThe micro-switch y'152 h'as `an upwardly 'projecting depressible button or plunger |52 disposed directlybeneath pus'h'rd 131 "-(Fig's. 4' and 5) for actuation by the latter, the lower end I"of the rod extending 'a' limited distance 'into an adjusting screw |63`iinounted thereon and provided-with an internally threaded adjusting Aferri-ile or nut |54 screwed upon said adjusting screw and directly engaging "the oval to'p of switch -lplunger |62. The adjusting nut |64 is adjusted 'by rotation Altoa position in which the plunger `Iii? sup trtsatlieweiglit-oi the lpush rod, erfassbar m, ring |25 anddiinpling sleeve |24, with'the latter projecting above the dimpling die |09 vlin. proper initial position rea-'dy for operation'. YIt is -tl-u's evident -that depression of the dini-plinglsleeve will be transmitted tothe push iod'an'd will eaus'e' the latter 'to depress the switch 'plunger and operate the switch. f

Referringto the circuit diagrams in --Fi`g's'. \10 to 13, the main line switch |65 is'st *closed as shown 'in Fig. 11 which effects" closure of the circuit vof current source y| 6 6 and relay j|641 through back vcontact '|168 and arm 'ti're :|69 of a second relay settingupthe VTapparat'us'Ifo'i' regular operation. Inotherwor'd's `closure lofthe main switchrst4 energizesrelay. f6?! "to cause the armature fil3ithereo'f to :make =contact '|'|"4 andv thereby close kvthe circuit including :pressure limiting or fdeflection plateI switch 11 mai-1d.end-pfY (yperatio'n iriaybe initiated -loy the operator "in depressi-ng 'pedal 'i'i io'fffoo't svi/itch T5 and 'U 'leby plftlyclos'lng the-starting SWilihfolt Ibybl ging "oo''itaots i'|72 together. VVhn the Work sheet 152 'fis placed li511 position between 'lille "pilot p'i-rs Ill-l and `E 'i (Figs. 1El and 9) 'with the i'l'efiln'd lil-Vet lholesA registering With the pilot pinsf,"thfe sheet rests on fthe ldiin-pliivig `sleve W4 "about l"pilot pin W6 (Figs. 8 and 9) and "a'sjthe 'sleeve ten-ds to "yel'l downwardly, the Weight lof lie sli'y'e't depressies E'the sleeve 'a'lin'ii'ted distance and 4till-is downward movement is immediately transmitted to' ring .i125 'and Zcrossb'ar 12"! and by lthe latter to push -rod `i371 and -as a result the latt'er depresses plunger i362 of mieroeswitch 152. Upo'n closure Iof 'the circuit thro'il'gl-l the sta j ing switch-es and relay "Ui i, the armature 169 of Athe latte' 'breaks Contact 5i158 (without any effect at this fl" et) f nd i'makes contact 7"W5 whiefh estab lish'es' fa lcircuit 4extending from main switch z|65, thlou" solenoid 55,*'ff1-ontcont'act 1|'l'5-and armature ittici frelay f|'|'i,=a1rih`ature 113 and -fr'ont oonta'ct fil'l of 'relay iBE, end-of-'st'loke switch d5, pressure limiting o'fr deflection plate switch ve eind Voltage4 sourde F555, when lthe Soleil'illl155 energized it drawsthe core li5 upward and raises the control valve 5d vto th'e'p'os'ition show-n in Fig. l l

In the raised position Y'of the control valve 554, 00th 'Valve hea-(ils 9715, l?? llelec'lf engage the iaip'p'er valve seats ill-8, *l 1in casing '53 but are separated from the lower valvese'ats 1785i, F82 respectively.' Pressure -iluid from :the outside source flows vinto 'passage |83, and passing -`lower valve seat 'M2 reaches passage figli communicat- "i'lg 'dliedtly With the fea-r piston han'be'l 435 and thus propels piston {3'73 and its 'rod `34 jfor wardly. A't lthe same time the front piston chamber ist is open to exnaustthrougli conti-uit les, passage |89, central valve' 'passage l`9l, past valve feat 118i 'and out through 'exhaust 'passage i512. As `the piston advances, rol-1ers -3'5 roll fforwa-rd along frail '35 and oncam lever 2f8,depressirigithe latter as diagranimaft'ic'ally shown in Figs.` l2 and 13. Cam lever 2-8 Vin turn depresses plunger and tool holder 21 (Fig. 9) with punch hol-der fili as well as punch jSii depending therefrom. the same vtime pilot 'portion lii oi' puiic'h E3 pushes pilot pin H55 down into'dimpii-ngfdie its and causes upper pilot 0| to descend a' short dis-e tance through 'the work sheet until 'the outer sleeve 93 ina-kes direct contact with y'the 'work Sheet. AS Vpilot pin I'H'f rests With its 'head HTF on fthe upper 'ends {iS-ofthe bifurcatedpinfsleeve l E9 and as the latter rests on washer 2l which iesilientl-y by vspring |522, 'the washer will yield and allow the pilot `pin to be `depressed to a low withdrawn position within the dimpling die, ready to rise again to original projecting posi-'- tion 'by Ithe urging of the spring |22 `as soon 'as the upper'pilot EDI is raised -at a later stage.

lit is tofbe noted that'crossbar iZ'i 'eXtends trans'-` v'ersely through 'the space separating the upper ends HB of bifurcated 'pin 'sleeve i it and rests directly on the uppe'riend vof push rouk si so :as to be :moved lby contacting' sleeve il 24 to depress rod |31 independently of pin sleeve ||9 and pilot pin H6 which are also independently movable.

While punch 83 continues to descend, the frusto-conical portion 98 begins to dimple the work sheet by projecting the metal beneath said portion into recess 4 of die |09 and simultaneously causing sleeve 99 to remain in contact with the work sheet under increasing pressure because said work sheet supported by the dimpling die obstructs further movement of the sleeve while the punch holder and punch continue moving, compressing pressure pad 85 above washer 89 against plate B8, and causing washer or ring 89 above sleeve 99 to shift to the upper end of groove 9| on punch holder 18. The resilient pad serves to prevent shocks as well as mutilation of the work sheet. continues until the upper inner sleeve 95 on the punch comes into contact with the iiat portion of said work sheet around the dimpled portion which is supported by the upper face |86 about the recess on the dimpling die.

When sleeve 95 strikes the flat supported portion of the work sheet as just stated, the resistance to further descent of the punch immediately increases to a very high counter-pressure because the sleeve is backed by the punch flange 94 and obviously cannot yield. The increase oi the resistance to further dimpling or`movement is then in fact so great as to stop the dimpling and instead impose an expanding strain on the yoke jaws which separates them sufficiently to raise fulcrum 61 on jaw 22 and thereby tend to raise deflection switch lever 66. However the deection plate 59 is not under any strain and therefore is not expanded with the yoke during the impling operation and its forward end 63 tends to prevent the short lower end 65 of the lever from rising; and thus the latter instead swings counterclockwise about its fulcrum, correspondingly swinging upper arm 68 of the lever against operating button 69 of micro-switch `10 (Fig. l) and thereby opening the circuit of said switch as diagrammatieally shown in Fig. l3.` This immediately cut-s off the current to valve solenoid 56 thereby allowing valve spring |93 to draw valve 54 downward to engage the heads thereof with the lower valve seats |8|, |82 and thereby reverse operation of the piston 33.

The opening of switch 10 also opens the circuit of relay |01 and allows armature |13 thereof to leavefront contact |14 and assume normal open position and thus open the same circuit at a second point. Relay |61 cannot be re-energized as long as relay |1| continues to be supplied with current through the circuit of foot switch 15 and work supporting switch |52, and thereby con tinues to hold the armature |63 away from back contact |68. The circuit of said switches must first be broken and then re-closed in order to reenergize relay |61 and start a new cycle of operation.

The control valve 54 having returned to its initial lower position as diagrammatically indicated in Fig. 13 and in which the piston as a result is about to return to initial rearward position, the operation is reversed as already noted, and the pressure iluid ilows from supply passage |83 past valve seat |19 and up through valve passage |91, through passage |89 and conduit |88 into front piston chamber |81, driving the piston rearwardly through the return stroke. The piston in turn drives lthe spentfluid in rear piston chamber |85 out through passage |84, down past The dimpling l 10 upper valve seat |18 and nally out through exhaust passage |92.

By the rearward or return movement of the piston and piston rod, the cam lever 28 is free to swing up from the operated position of Figs. 2, 12 and 13 to initial idle position (diagrammatically indicated in Figs. 10 and` 1l) and the plunger 26 with set holder 21 and associated punch holder and dimpling punch will rise to the initial position of Fig. 8, freeing the work; sheet for removal by the operator. The pilot pin ||6 is also raised to initial position byV spring |22 urging washer |2| upward until it is stopped against the bottom of die holderor dolly |03, the washer raising pin sleeve I9 and with it the pilot pin. As soon as the work sheet is removed from the machine or from the position in which the dimpled portion is dissociated from the dimpling die, contact sleeve |24 is free to rise with ring |25, push rod |31 and switch plunger |62, which thus opens the work supporting microswitch |52. For this purpose the latter is preferably provided with interior resilient means (not shown) having sufiicient strength to raise plunger |52 when relieved of the weight of the dmpled sheets. As soon as the starting switch circuit is broken, either by relieving the switch |52 of the weight of the workpiece or by release of the foot switch 15, relay |1| is de-energized, restoring armature |69 into engagement with back contact |68 and permitting a new cycle of operations to commence, whenever the starting switch circuit is again closed.

If desired the operator `may disable the deection switch 10 by turning the adjusting knob 10a (Fig. l) to create an excessively wide gap between deflection switch lever arm 68 and the associated trigger or switch button B9. In that condition of the apparatus, the piston rod. 34 is permitted to continue to advance until the forward end strikes the lever 43 to open the end-ofstroke switch 45. This has the same effect on the solenoid circuit as does the opening of deflection switch 10. In the use of the end-of-stroke switch, the operator predetermines the `maximum distance of approach or penetration of dimpling punch 83 with respect to recessed dimpling die |09. This distance can be varied, to suit the requirements of different workpieces, by turning the knob |43 (Figs. l, 2, 5 and 6) to regulate the height of the dolly spindle |01.

Proceeding now to consider the underside dirnpling, it will be noted that certain of the operating parts and tools supported by the yoke jaws orinverted or modified as shown in Figs. 6 and '7, about to be described, in contrast with the corresponding parts of Figs. 1, 2, 3, 5, 8 and 9, and are even reduced in number. However the set holder 21 in upper jaw 22, and bushing` |08, crossbar |21, switch push rod |31 and microswitch |52 etc., associated with lower jaw 23 are unchanged, while thecircuits, relays and switches also remain in principle as already described in connection with Figs. 1, 4 and 8 to 13. Thus the vwith the shank and preventing the holder from turning. The dimpling die |09 in inverted position has shank lll thereof secured in bore |98 l 1 of the die holder by set screw lilil while the working face |85 and recess lili face downwards.

In the lower jaw 23 the hollow puncliadiusting screw or sleeve 2li! replaces `the, dolly spindle or die adjusting sleeve im oi the former structure and is screwed adjustably into bushing Hi8, the lower end with the-extension 262 (Fig. 6), scale 2M and adjusting knob 2M inail respects resembling the corresponding parts in Figs. 4 and 5. The shank 2% of a punch holder 266 extends down into bore 2551 of adjusting sleeve 29| and is secured in place by the tubular screw ist through which the switch push rod 431 extends, this screw terminating in the head ill! at the bottom (Fig.

above by split retaining ring 39 while beneath plate 88 the adjusting nut ,92 is screwed up on thread 269 onthe punch holder to proper adjustment of the pressure pad, which resiliently urges ring 89 to the upper end of a wide groove 2li in which it is slidable. Upon the upper end of the punch holder 2&5 is mounted the dimpling punch 83 with iiange 94 thereof resting on the punch holder and shank Sil secured in bore 2|2 by a set screw 2|3 and the pilot portion lill with associated frusto-conical dimpling portion 9,8 projecting upwards toward the dimpling die. A slidably mounted contact or skin supporting sleeve 214 slidably surrounds cylindrical portion 2% on the punch holder and ange 9?! of the punch and rests on the short sleeve or ring E which in turn is supported on crossbar E21 which extends transversely through slot 2 l 5 in the punch holder and into bottom slots I2@ in the ring and rests intermediately on the upper end of push rod I3?. Above punch ange S4 the innery sleeve 95 is secured to the punch body by set screw 36 and accurately spaced from the flange by sleeve shim 91, the punch, sleeve and shim each being one of a series of different sizes selected and grouped together for each size of dimple to be applied to the work sheet.

The crossbar l|21 in normal idle position is located a suicient distance above retaining ring 89 to allow contact sleeve 2|4 to depress the crossbar and thereby operate the push Vrod |31 in order to actuate microfswitch |52 without said crossbar being stopped short by said ring 89 when a work -sheet is placed in position on said sleeve |24 with a rivet hole registering with pilot portion IUI of the punch. The resulting closure of switch `I 52 starts a cycle of operation which electrically is exactly as previously described with reference to the circuits shown in Figs. 10 to 13 but mechanically differs byv certain details as follows. s

Inasrnuch as the dirnpling is now to be accomplished vupwardly in the same direction in which punch pilot lill projects, it is unnecessary to depress or otherwise di-spose of this pilot during operation, and hence, when the plunger and thus also set holder 21 descend due to the forn ward travel of the piston, the die holder and dimpling die |09 will approach the punch 83 below and the work `sheet |'02 resting on contact cess as a result of the working face |86 ofthe die forcing the work sheet down upon inner sleeve 95, meanwhile depressing the outer contact sleeve to `the same general level as;sleeve 95. This operation is believed to be clearly understood from Figs. 6 and 7 when considered in the `light of the description and showing of Figs. 8 and 9. The outer sleeve 2M having already been suiciently depressed by the 4weight oi the .work sheet to depress rod |31 and thereby operel ateswitch |52 `for initiating the dimpling operation, the descent of the dimpling die onv a work sheet depresses sleeve 2M still further `to the inner sleeve level as just mentioned, thereby causing sleeve or ring 25 associated with the crossbar to bear downupon retaining ring 89 and washer` 81 to -compress pad 86 and also shift ring 89 downward in its groove 2li on the punch holder. The pressure thus exerted on the work sheet around the portion` being dimpled serves primarily to prevent distortion and definitely to keep the sheet at during dimpling, and also when the pressure is great enough to spring the yoke jaws apart and operate the deflection plate switch and reverse operation for releasing the dimpled work sheet and thereafter repeating the cycle at will.

In both the topside and the underside dimpling, the pressure pad causes the pressure applied around the portion of the work sheet being dimpled to rise gradually from below that suiicing to `lreep said portion fiat up to the high expanding pressure springing the yoke and effecting operation of the deflection switch plate. This featureeliminates shocks and tends to avoid marring, distorting or otherwise damaging the` work sheets during the later stages of the operation.

Disclosures related to that of the present invention appear in copending applications of Howard R. Fischer and James A. Roberts, Serial No. 51i .068, filed December 13,1943, and Serial No. 686,406, filed July 26, 1946.

What is claimed is:

1. In a press having a pair of jaws spaced apart and individually supporting mutually opposite tools for `forming work sheets, operable means for bringing one of the tools toward the other tool upon a work sheet to form the latter and for separating the tools from each other, and movable control means adapted in one position Vto initiate `operation o1 the operable means and in another position adapted to cause reversal thereof to separate said tools, the combination of an electricalactuating means connected to the control means and capable of moving the latter from the one position to the other, an electric switch means for lcontrolling the circuit of the electrical actuating means to allow current from a current source to iiow through and actuate said electrical actuating means and thereby move said operable means, a switch operating member movably associated with said other tool and projecting a suflicient limited distance toward the respectively opposite one tool to be moved by a work sheet when placed in proper forming position in relation to said other tool, a foot switch associated with the mentioned circuit for initially closing it at will, means communicating vthe movement of the switch operating member to said 4electrical switch means to effect closure of the latter, and automatic means Aarranged to be actuated in response to a predetermined pressure between the tools for causing said control means to reverse operation of said operable means for separating said tools and releasing the work sheet upon completion of the forming of the latter.

2. A press according toclaim 1, in which the last mentioned automatic means includes a reversing switch associated with the circuit and capable upon being actuated of causing the control means to effect reversal of the operation of the operable means to terminate the forming operation, and operable means responsive to a predetermined pressure between the tools for automatically actuating the reversing switch upon completion of the forming of the work sheet.

3. In a press having a pair of jaws spaced apart and provided with support means for individually supporting mutually opposite tools for forming work sheets, operable means for bringing one of the tools toward the other tool upon a work sheet to form the latter and for separating the tools from each other, and movable control means adapted in one position to initiate operation of the operable means and in another position adapted to cause reversal thereof to separate said tools, the combination of an electrical actuating means connected to the control means and capable of moving the latter from the one position to the other, an electric switch means for controlling the circuit of the electrical actuating means to allow current from a current source to now through and actuate said electrical actuating means and thereby move said operable means, switch operating means for said switch means including an exposed movable member mounted exteriorly adjacent to and relatively movable with respect to said other tool and capable of being moved by a work sheet when placed in proper forming position relatively thereto, an interior switch actuating member mounted within the support means for and in axial alignment with one of said tools for movement in unison with said exposed movable member to directly actuate and close said electric switch means and thereby cause operation of said operable means, and an intermediate' member extending from an exterior portion to an interior portion of the Support means for the one tool in eiective position to transmit the movement of said exposed` movable member to the interior switch actuating member to actuate said electric switch means by movement of said exposed movable member, and further electric switch means also associated with said circuit and operable at will for initially closing the latter.

4. In a press having a pair of jaws spaced apart and provided with support means for individually supporting a, pair of mutually opposite tools for dimpling work sheets, one of the tools being a hollow dimpling die and the other a frusto-conical dimpling tool terminating in a pilot portion adapted to project into the die in operated position, operable means for bringing one of the tools toward the other to dimple the work sheet between them, the combination of movable' control means for initiating operation of the operable means in one position and in another position effective to cause reversal of said operable means, a'movable contact member mounted ad- `iacent to the exterior of one tool and the support means thereof and capable of being moved by a work sheet when placed in position to register a, rivet hole therein with said pilot portion, an interior actuating member movable within the last mentioned support means, and an intermediate movable member extending from an'exterior portion to an interior portion of said last support means in effective position to communicate the movement of the movable contact member to the interior actuating member in order to move the latter in unison with said movable contact member, and means actuated by said interior actuating member effective to cause operation of said control means with consequent operation of the tools -to dimple said work sheet.

5. In a press having a pair of jaws spaced apart, one jaw having a substantially stationary support means thereon supporting a dimpling tool, a second support means mounted on the other jaw and movable with respect to the latter toward and from the rst mentioned support means, a second dimpling tool mounted on said second support means, the combination of a resilient cushion member forming apressure pad mounted on one of the support means, a pilot portion projecting upon one tool toward the other, the said dimpling tool `with the pilot portion having a flange, a tool sleeve removably secured to said tool in axial alignment with the flange, a shim mounted on the tool between the tool sleeve and the flange and removable with the ltool sleeve to be replaced by anothershimwhereby to alter the tool to dimple dilerent gauges of metal, a movable contact member disposed exteriorly adjacent to the tool about theange and the tool sleeve and normally occupying a position wherein a portion projects beyond said tool to be movable by a work sheet when placed in position to register a rivetvhole therein with said pilot portion, means for operating saidmovable support means and associated tool, the resilient cushion member being associated with the support `means of the tool provided with the pilot portion and serving to cushion the movement of the contact member when the latter makes contact with the work sheet during the dimpling operation while said work sheet rests against the tool opposite said pilot portion, andmeans 4for automatically stopping the dimpling movement of said movable support means and associated tool when the work sheet is dimpled.

6. In a press having a pair of jaws spaced apart,

one jaw having a substantially stationary support means thereon supporting a dimpling tool, a second support means mounted on the other jaw and movable `with respect to theI latter toward and from the iirst mentioned. support means, and a second dimpling tool mounted on said second support means, the combination of a resilient cushion member forming a pressure pad mounted on one of the support means, a pilot portion projecting upon one tool toward the other, a rigid stop member removably mounted on the latter tool to form a stop for said tool against the work sheet, a shim retained on the tool by the stop member and removable with the stop member to be replaced by another shim whereby to alter the tool to dimple dilTerent gauges of metal, a movable contact member disposed eXteriorly adjacent to the tool on the latter and normally occupying a position wherein a portion projects beyond said tool tobemovable by a work sheet when placed in position to register a rivet hole therein with said pilot portion, means forI operating said movable support means and associated tool, the resilient cushion member being associated with the support means of the tool provided with the pilot portion and serving .to cushion the movement of the contact member when 15 thelatterma-kes JContact with the Awork sheet during the dimpling operation while said work sheet rests against the tool opposite said pilot portion, vand means for automatically stopping the dimpling Operation -when said rigid stop member eng-.ages against :said work sheet.

7. `In a press having a pair of jaws spaced apart, one jawhaving asubstantially stationary support means thereon supporting a dimpling tool, a second support means mounted on the other jaw and movable With respect to the latter toward and from the first mentioned support means, and a second dimpling tool mounted on said second support means, the 'combination ci a I,pilot portion rigidly mounted upon one tool andadapted during dimpl-ing to project into the other tool, an exterior sleeve slida-bly mounted upon the support means of the tool having .the pilot portion, a cushion `member mounted on the last mentioned support means in elective position to urge the sleeve to project va limited distance beyond the tool on said support means, `a stop portion rigidly associated with said las-t mentioned tool adapted to engage against the work 'sheet at the end of the dimpling step, means to initiate operation and cause movement vof the movable support means and its associated -dimfpling ,tool to dimple the work sheet, and strain-responsive means between the jaws effective to terminate operation when `a predetermined high dimpling pressure of lthe tools is attained upon said Work sheet.

8. In a lpress having a pair of jaws spaced apart, one jaw having a substantially stationary support means thereon supporting a dimpling tool, a second support means mounted on the other jaw and movable with respect to the latter toward and from the rstmentioned support means, and a second 4dimpling tool mounted on said second support means, the combination of operable means -for initiating operation and causing movement .of the movable Support means and associated dimpling tool toward the other tool to dimple awork sheet, a pilot :portion rigid with one tool and adapted to project into the other tool during dimpling, an exterior sleeve slidably mounted on .i

the support means of the tool having the pilot portion, a cushion member mounted on the last mentioned vsupport means in effective position to urge the sleeve to project a limited distance beyond `the tool on said support means, a stop por- .tion rigidly vassociated with the last mentioned tool `adapted to engage against the work sheet at the end of the dimpling operation, operable control means associated with one jaw for initiating the dimpling operation, a :movable push rod slidably associated with said one jaw in effective position to operate said ,operable control means, means movably carried upon the latter jaw intermediate said push rod and said sleeve to be effective -to transmit initial movement of said sleeve to said push rod, the resilientcushion member mounted on the mentioned support means on said one jaw being disposed in the path of movement of the intermediate means and compressed by the ,latter when the sleeve is forced down upon the intermediate means by the other or opposite dimpling tool.

3 9. Ina press having `a pair of jaws spaced apart, one jaw having a substantially stationary support means thereon supporting a dimpling tool, a second support ,means mounted on the other jaw and movable with respect to the latter toward and from the rst mentioned support means, and .a second dimpling tool mounted on said second support means, the combination oiV a pilot porlil) tion rigidly mounted upon one tool and adapted during dimpling to project into the other tool, an exterior sleeve slidably mounted uponV the support means of the tool having the pilot portion, a cushion member mounted on the last mentioned support means in effective position to urge the sleeve to project a limited distance beyond the tool on said support means, a stop portion rigidly associated `with said last mentioned tool adapted to engage against the work sheet at the end of the dimpling step, a ,stationary deilection member having one portion attached to one -o-i said jaws, a stop switch r:for .terminating operation when actuated, and a further portion upon said deflection member eiiective to actuate said stop switch upon attainment of a predetermined high dimpling pressure exerted by the tools on the Work sheet.

10. In a press having a pair Yof jaws spaced apart, one jaw having a substantially stationary support means thereon supporting a dimpling tool, a second support means mounted on the other jaw and movable with respect to the latter toward and from the nrst mentioned support means, and a second dimpling tool mounted on said second support means, the combination of operable means for initiating operation and causing movement of the movable support means and associated dimpling tool toward the other tool to dimple'a work sheet, a pilot portion rigid with one tool and adapted to project into the other tool during dimpling, an exterior sleeve slidably mounted on one support means and projecting a limited distance beyond `the tool thereof in a position to be moved by a work sheet placed in proper dimpling relation with said tool, control means mounted on the latter support means adapted when actuated to cause operation of said operable means, a push rod movably mounted within said latter support means with one end adjacent to a portion of said control means in effective position to operate the latter, a bar having a portion disposed adjacent to the other yend of said push rod, an annular member movably mounted on said latter support means vadjacent to one end of the exterior sleeve and to said bar capable of. transmitting movement of the exterior sleeve in one direction to said bar and push rod, means rigidly associated with the last mentioned tool for limiting the dimpling of the work sheet, and means upon said press for stopping the operation of said operable means when the work sheet has been dimpled.

11. In a press having a pair of opposite jaws spaced apart With one jaw provided with a stationary` dimpling tool including a die and the other j avv with a movably mounted dimpling tool terminating in a pilot portion. adapted to extend into said die in mutually engaged condition of said tools, and operable means for moving said movably mounted tool toward the other tool and for separating the same therefrom, the combination of control means for initiating operation of said operable means, a depressible pilot pin slidably associated with said die, means resiliently maintaining said pilot pin normally projecting from the die toward said pilot portion in a position allowing the latter to depress said ypilot pin into said die, a movable contact member disposed eXteriorly of said die, a push rod slidably associated with a, portion supported by the rst mentioned jaw with one portion of the push rod effective to actuate the control means upon movement of said rod, an intermediate member interposed between another portion of said push rod and said contact member to communicate the `movement of the latter tothepush rodi and thereby actuate `said control means, and means for automatically terminating the dimpling operation and separating said `movably mounted tool from the other tool when thework; sheet has been dimpled in order to release the latter and allow the pilot pin to resume its `initial projecting position on the die. l l

12. In a press having a pair of opposite jaws spaced apart with one jaw `provided with a sta-` tionary dimpling tool including a die andthe other jaw with a movably mounted dimpling tool terminating in a pilot portion adapted to extend into said die in mutually engagedcondition' of said tools, and operablemeans for moving said movably mounted tool toward 'the other `tool and for separating the same therefrom, the combination of control means for initiating operation of said operable means, a depressible pilot pin slidably associated with said die, means resili-,VZO

ently maintaining said pilot pin normally project" ing from the die toward said pilot portion in a position allowing the latter to depress said pilot pin into said die, a movablecontact member disposed eXteriorly of said die, a push rod slidably associated witha portion supported by the firstl mentioned jaw withV one portion of the push rod effective to actuate the control means upon movement of said rod, an intermediate member interposed between another portion of said push rod.

and said contact memberto communicate the` movement of the latter to the `push rod and thereby actuate said control means, an annular member movably supported on the second or other jaw, a resilient cushion member also supported,- on the latter in `eifectivefposition toresiliently'" resist movement of said annular member and normally urge the latter to project a limited distance toward the die in order to cushion the engagement of said annular member with the work sheet a stop rigidly associated with the `dimpling tool to stop the latter against said work sheet, and means for automatically terminating the dimpling operation and separating said movably mounted tool from the other tool when the last mentioned stop exerts a predetermined high pressure on the work sheet.

when the latter rests on said die during dimpling',`

13. A dimpling machine comprising a punch element, a recessed die element arranged coaxially therewith to receive sheet metal "therebetween, a pilot pin coaXially mounted on one of said elements and adapted to enter a preformed `hole in the sheet metal for centering the workr forming elements relative to the preformed hole,a starting trigger positioned to be actuated automatically supporting member adjustably affixed tothe other jaw by means of a threaded connection, a dimpling die in the die supporting member, means operable by fluid pressure for bringing the punch toward the die, and uid control valve means adapted when in one position to initiate operation of the operable means and in another position to cause the reversal thereof to allow movement of the punch away from the die, the combination of a solenoid associated with said valve and capable of moving the latter from one position to another, an electric switch means for controlling the circuit of the solenoid,l a switch operating sleeve surrounding the die supporting member and movable with reference thereto, said sleeve extending beyond the die in a direction to protrude beyond the forming face of the die, a supporting element for the switch operating sleeve surrounding the die supporting member, a transmission member associated with the sleeve supporting element and extending through the center thereof, a transmission rod coaxial 'with the sleeve to support the transmission member, the sleeve supporting element, and the sleeve, and a plunger for the solenoid controlling switch adapted, while the switch is open, to support the assembly comprising the transmission rod, the transmission member, the sleeve Supporting element and the switch operating sleeve.

15. A dimpling machine comprising a pair of spaced jaws, a dimpling punch in one jaw, die supporting means adjustably affixed to the other jaw kby means of` a threaded connection, a dimpling die in the die supporting means, means operable by fluid pressure for bringing the punch toward the die, and fluid control valve means adapted when in one position to initiate operation of the operable means and in another position to cause the reversal thereof to allow movement of the punch away from the die, the combination of a solenoid associated with said valve andcapable of moving the latter from one position to another, an electric switch means for controlling the circuit of the solenoid, a depressible pilot pin projecting through the die and `slidably associated therewith, a pilot pin supbeyond the forming face of the die, a supporting element for the switch operating sleeve surrounding the die supporting means, a transmisl sion member associated with the sleeve supporta predetermined pressure between the die and ing member and extending through the center thereof and through the slot of the pilot pin supporting member, a transmission rod connected to the transmission member, and a plunger for the solenoid controlling switch, the arrangement of the switch operating sleeve, the switch supporting element, the transmission member, and the transmission rod being such that they are moved as a unit to close the solenoid controlling switch when a work sheet is disposed in proper work forming position relative thereto, and the arrangement of the pilot pin, the supporting member therefor and the resilient support for said support being such that they move independently of the switch operating assembly.

16. In a dimpling machine of the class described, a solenoid to actuate a valve, a switch in the electrical circuit to the solenoid, a die holder F19 arranged in a jaw, a die having allongitudinal central aperture,-a support therefor mounted on the die holder Vand having a longitudinal bore and radially disposed slots connected to the bore,

a depressible pilot pin extending through the die f aperture and the die support bore, a pilot pin supporting member having a longitudinal slot adapted to register with the die support slots, resilient means in the die holder to support the pilot pin supporting member, a switch operating` sleeve surrounding the die, Aa sleeve supporting member, a 'crossebar mounted'in the sleeve supporting member and extending through the slot in the pilot pin supporting' member and the slots in the die supporting member, and a transmission redco'nnected to the cross pin, the sleeve, `the support-ing member therefor, the cross pin, and the transmission rod being arranged Yto `move as a unit to tran-smit metionimparted to the sleeve by theweight of a work sheet disposed thereon to lclose the switch to the solenoid, and the pilot pin, its supporting means, and the resilient supporting mean-s being arranged to move as a unit independently "of the switch operating mechanism.

1'7. In a pressfof the class wherein spaced jaws carry a stationary punch and a movable die actuated by fluid pressure Controlled by an elec-` trically operatedvalve andwherein the switch i controlling the electric circuit is operated by the weight of a work 'piece disposed on the stationar'y punch, in combination, a dolly supported in a jaw, a punch rigidly mounted on the dolly, "a sleeve' mo'vably associated with the dolly', support means or's'aid sleeve surrounding the dolly, an intermediate transmission member extending from van exterior to an interior portion of said support means, transmissionmeans connected to the intermediate member, the foregoing sleeve,

supporting means, vintermediate transmission member, and the transmission means beingl associated to move'a's a ufnit when a work sheetis disposed for operation upon the sleeve vtherebyY to actuate the valve switch, a plunger for the switch 'arranged adjacent the transmission means and adapted to support-said unit in initial` position, resilient means -i-n the switch adapted to support the plunge nd unit iin initial position and to return the plunger'and unit to initial position upon theremoval vof the work -sheet therefrom, and resilient cushion means mounted on the dolly in the path of the intermediate transmission member to oder 'resistance to the rlatter and hence to the sleeve when the 4latter 'is forced down upon the intermediate ineans by the ymovable die therevby to create a reactive force to 'maintain the work sheet in planar position when under operative pressure.

185A combination, `accordmg to claim ,17,

wherein theresilie'nt'cushion means comprises Van annular!memberv of resilient material, a supporting lwasher therefor, aretaining plate, a retaining ringassociated with the dolly, and an adjusting ring threadablymounted on the dolly,

the retaining ringandthe adjusting ring being arranged oppositely with respect to the ring to vary the resistance of the cushion.

'19.'In a machine` of the class described, a

hold-down device comprising a punch holder, resilient kcompression means mounted on the punch holder, means to retain the compression means in operative position, means to preload the compression means to a predetermined deadapted for limited longitudinal movement in` a slot fon the punch holder, means to preload the compression means to `a predetermined degree ofY compression, a sleeve movably mounted yon the punch holder 'and spaced from the punch, support means. for-the sleeve arranged between thev lsleeve and the -compression means, Y and switch operating means connected to the sleeve support, said sleevebeng vmovable by the weighty v'otawvorli sheet when the latter is placed in proper forming position to transmit 'motion Y, through the,v sleeve support to the switch operof thispatent;

ating means thereby -toactuate a switch and being further adapted thereafter to maintain the work sheet in planar position by the transmis- :sion 'of reactive force from the lresilient compres sion means throughthe lsleeve support means during K the pressing operation.

. HOWARD R.. FISCHER.

REFERENCES lerr-an The following references are of record in the '-gUNfITIED `STATES PATENTS Number Name Date 1,454,777 Wai-ker May e, 1923 11,958,869 v stever L May 15, 1934 uMernrma'n sept. 7, 1943 

